Gas operated semiautomatic or fully automatic firearms use a portion of the propellant gas diverted from the barrel bore for automatically cycling the action each time a round is fired. Such firearms, including AR-pattern firearms, typically use a gas block that is mounted over a gas port in the barrel. The gas block may be mounted to the barrel and secured in place over the gas port, such as with set screws or pins. In a direct impingement gas system, a gas tube carries a flow of gas pressure from the gas block to the upper receiver where it is directed into a bolt carrier assembly. Connection of the gas tube to the gas block is commonly achieved by pressing a small roll pin through a cross bore in the gas block that aligns with openings adjacent the forward end of the gas tube. This holds a port in the wall of the gas tube in alignment with an internal gas passageway in the gas block.
Holding a gas block securely while holding the gas tube in the proper position and simultaneously driving a roll pin through the cross bore to secure the gas tube can be a challenging task. Gas blocks do not typically have flat sides, making it difficult to lay it on a flat surface during this installation process. Clamping the gas block in a vise can mar the finish or otherwise damage the gas block. Moreover, gas blocks come in a variety of external sizes, styles, and shapes, some being low profile, some including an integral front site, and others including an accessory mounting rail. Accordingly, a wide variety of jigs or fixtures would be needed to adapt to the varies external sizes and shapes.
A “universal” fixture that is simple, versatile, effective, and inexpensive is needed.